1. Field of the Invention
The invention relates generally to powered surgical tissue cutting devices. More particularly, the invention relates to mechanisms for attaching tissue cutting devices to handpieces. Still more particularly, the invention relates to wrenchless collet mechanisms for attaching tissue cutting devices to powered handpieces without the need for any additional tools or adapters.
2. Description of the Prior Art
It is often necessary to use powered tissue cutting tools in order to perform surgical procedures. Such tools generally comprise a handpiece which cyclically moves a tissue cutting device such as a blade or burr in some oscillating or reciprocating manner. The handpiece generally includes a pneumatic or electric drive motor having an output shaft to which the cutting device is attached, the shaft being axially aligned with a drive axis of the handpiece. As used herein, the term "drive axis" refers to the axis of the motor output shaft through which power is delivered from the motor. The handpiece may be a "pencil" type handpiece in which the body is elongated and the drive axis is aligned with the axis of the body or a pistol-grip type of handpiece in which the drive axis is aligned in a chosen direction relative to the grip. The drive motor of the handpiece produces a driving force which reciprocates the output shaft and cutting device either longitudinally, i.e. linearly along the drive axis (like a saber saw), or arcuately in a plane perpendicular to the drive axis. Handpieces utilizing the former type of action are generally referred to as reciprocating saws while those utilizing the latter action are generally referred to as oscillating saws. In some cases an oscillating saw may transfer the oscillating drive motion so that it is cyclical within a plane parallel to the axis of the elongated body of the handpiece. A sagittal saw is a type of oscillatory saw in which the cyclical reciprocating action is in a plane aligned with the drive axis.
In all instances, numerous tissue cutting blades or burrs or other devices (all collectively referred to herein as "blades") are adapted to be secured to the handpiece via a collet mechanism which is utilized to selectively attach and release a desired blade. A variety of different cuts can be made with a single saw depending upon the shape of the blade. For oscillating saws, the blades are often in the form of a flat, elongated body having a cutting edge (e.g. teeth, abrader, etc.) at one end and a hub at the other end, the hub being shaped and adapted to fit the particular collet. Such flat blades are used to make cuts in a plane perpendicular to the drive axis. An oscillating saw may also be used for effecting cuts in a plane parallel to the handpiece axis by attaching a transverse hub to a flat blade. A crescentic blade having a curved instead of a flat body may be used for curved cuts. The body of a crescentic blade has teeth (or another cutting edge) at its distal end which follow the shape of the arcuate body so that as the blade oscillates about the axis, the teeth follow an arcuate pattern having a center of curvature on the axis. Some flat blades may have the cutting edge at an angle to the blade body to make cuts in an angled plane. Angled blades may have an axially elongated body either on or off the blade axis. That is, the proximal end of the blade body may have a transverse hub or it may simply be attached in-line with the drive axis. The resulting cut is arcuate and facing away from the axis.
Many blade collets utilize a threaded stud axially extending from the output shaft and a nut adapted to engage the stud to clamp the blade hub to the handpiece. These collets generally require the use of separate wrench to turn the clamping nut. Since it is desirable to avoid extra tools in a surgical setting, some collets eliminate the need for a separate tool by utilizing a nut (e.g. a wingnut) that can be manipulated without tools. Other collet designs utilize a spring actuated, longitudinally movable clamping head having longitudinally extending locking pins for engagement with corresponding holes in the blade hub. The clamp head in such designs is movable to place the collet into an open position for receiving a blade and into a closed position for clamping the blade between the head and a base surface. Such designs are referred to herein as "wrenchless" designs and are generally preferable to other collet mechanisms which require the use of separate tools.
Adaptation of an axially elongated blade such as a crescentic or an angled blade to an oscillating saw is achieved in some prior art devices by providing the elongated body of the blade with a transverse hub and adapting the transverse hub to mate with an in-line wrenchless collet which can also receive a flat blade hub. This enables the saw to make cuts either in a plane perpendicular to the handpiece axis, in a plane angled with respect to the axis or along a curve having its radius of curvature on the axis. However, such axially elongated blades are often subjected to lateral loading during use such that the transverse hub acts against the spring-loaded clamp head. That is, wrenchless collet mechanisms known in oscillating saws often rely on spring pressure to securely hold a blade hub between a clamping head and a base surface. During oscillatory motion any lateral forces applied to the saw blade cause the transverse hub of the blade to lift the clamping head from its closed position, thereby compromising the security of the blade attachment. Additionally, such transverse loading may induce blade vibration and adversely affect cutting performance.
Another known method of adapting angled and crescentic blades to an oscillating saw relies on providing an axially aligned shaft at the proximal end of the blade body. Such a system is utilized in the COMMAND 2 Oscillating Saw available from Stryker Instruments, 420 E. Alcott Street, Kalamazoo, Mich. 49001. This system adapts such blades for use with a conventional oscillating saw having a clamping head transverse to the axis of the handpiece, the head having a plurality of circumferentially arranged and longitudinally extending pins facing proximally (toward the handpiece body). The clamping head is supported on an axially aligned shaft and is movable into an open position in which the head is spaced from the body of the saw and a closed position in which the head is urged under spring pressure proximally against a base surface adjacent the body of the saw. Since the saw is usable with flat blades, an adapter interface is provided for use with axially elongated blades such as angled and crescentic blades. While this saw has a wrenchless collet when it is used with flat blades, the adapter required to make this saw suitable for angled and crescentic blades makes this a tool-dependent system. The adapter has a proximal end with a semi-circular flange having a plurality of radially extending slots adapted to engage the pins on the clamping head. The distal end of the adapter is provided with an axial bore adapted to receive the axial shaft proximally extending from the angled or crescentic blade and a set screw is used to secure the shaft to the adapter. This design has the same limitations as the aforementioned prior art devices since any lateral forces exerted upon the elongated angled or crescentic blade will be translated to the semi-circular flange of the adapter and will have the same effect of compromising the security of the clamping structure. Also, this design requires not only a separate tool but an additional piece which adds to equipment present during a surgical procedure.
It is accordingly an object of this invention to produce a collet system adapted to securely hold a tissue cutting device to an oscillatory saw.
It is also an object of this invention to produce a wrenchless and adapterless system for securing a surgical blade to a powered handpiece.
It is also an object of this invention to produce a wrenchless and adapter-less system for securing angled and crescentic blades to a powered handpiece.
It is yet another object of this invention to produce a system for attaching tissue cutting devices to powered handpieces without the necessity for auxiliary tools.
It is an additional object of this invention to produce a wrenchless system for securing a surgical blade to a powered handpiece so as to decrease blade vibration induced by lateral loading on the blade.